Zep - we use limestone here often, but maybe because quarries are so close by it greatly reduces the price/ton. On my easement road I started with 3-4" chunks, as they work themselves down into the clay I slowly incorporate smaller sizes and eventually I'll finish with a 1-2" size. If you're using gravel, it seems to me the way to go is to use pea gravel first, then graduate to the smaller gravel sizes, but I'm certainly no expert.